Recently on Facebook, Thomas J. Kwiatkowski Jr. called me on my usage of the word “scleras”. The sclera is the white part of the eye, and it’s taken from the Latin. In Latin, its plural would be sclerae, and that it how it is often pluralized in medical texts (doctors being familiar with Latin pluralization rules in general). But I had checked Merriam-Webster’s website prior to my posting, and it listed no special plural for it, leaving the standard plural “scleras” implied.
Now, there are some dictionaries that list the Latin-style plural. The American Heritage Medical Dictionary is one, but even it lists both the English-standard “scleras” along with “sclerae”. And there’s a wonderful tool that can show that this is probably the right way to go, if you’re going to create a descriptivist dictionary.
Google’s Ngram Viewer lets you see how different alternatives have been used in actual publication throughout the years. And, except for a period in the 1860s, “sclerae” definitely outpaces “scleras” in English publications. So I won’t say either is wrong.
I will continue to use the less-common “scleras”, though. English has enough inconsistency that I see no reason to use non-standard plurals when standard plurals are accepted. I don’t say “alumnuses”, for example, as it has barely-there use—but in that case, I’d probably opt for the less formal “alums” rather than “alumni”, if the outlet permitted the drop in formality. But I opt for “vertexes”, “cherubs”, “dogmas”, and “ninjas” over “vertices”, “cherubim”, “dogmata”, or “ninja”; both forms are in measurable use, so why not adopt the word fully into English?